Wide band and color cathode ray tubes and systems



Oct. 4, 1966 D. M. GOODMAN WIDE BAND AND COLOR CATHODE RAY TUBES ANDSYSTEMS 4 Sheets-Sheet 1 Original Filed March 20, 1959 RGBGR FIG. 2

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WIDE BAND AND COLOR CATHODE RAY TUBES AND SYSTEMS Original Filed March20, 1959 4 Sheets-Sheet I5 /43/ GREEN BLUE M8 FIG. I4 /44 1/ n l r l Q L/40 I '1 H 55 /54 RED VIDEO 52 FIG. l6 FIG. I? FIG. l8

INVENTOR.

DAWD M GOODMAN BY y/(LL A TTOIENEY 1956 D. M. GOODMAN 3,277,235

WIDE BAND AND COLOR CATHODE RAY TUBES AND SYSTEMS Original Filed March20, 1959 4 Sheets-Sheet I V 2o5 a l 1243 1 2 h I 204 I I NVENTOR.

DAV\D M- GOODMAN A 1- ra/ausy 3,277,235 WIDE BAND AND COLOR CATI-IODERAY TUBES AND SYSTEMS David M. Goodman, 3843 Debra Court, Seaford, N.Y.Qliginal application Mar. 20, 1959, Ser. No. 800,854, now Patent No.3,081,414, dated Mar. 12, 1963. Divided and this application Feb. 8,1963, Ser. No. 257,335 20 Claims. (Cl. 178-5.4)

This invention relates to directed ray tubes and systems that utilizeelectro-magnetic index signals to indi' cate the position or intensityof the directed rays in such tubes. More specifically, this inventionrelates to cathode ray tubes and systems that may be used in colortelevision. This application is a division of my co-pending application,Serial No. 800,854, filed March 20, 1959, now US. Patent 3,081,414.

In general, in television systems an image to be presented is producedby scanning an electron beam in a raster pat-tern across a target screenand by controlling the intensity of excitation of the target screen. Theraster pattern usually is rectangular in shape. It is known that, insystems of the type under consideration, controlling the electron beamshape and size, and its horizontal sweep, is often times advantageous.It has been attempted thereby to achieve color registration and purity.

One of the objects of this invention is to present additional novelmethods and techniques, especially for use in color television, thatprovide a degree of control of the electron beam not heretoforeattainable. This invention achieves this control by shaping the electronbeam and suitably delaying the sweep of the electron beam across atarget screen as a function of the intensity modulation imparted to thebeam. The electro-magnetic index signals, generated as a consequence ofbombardment of the target screen by the controlled beam, then aremanipulated to provide numerous improvements in circuit operation.

Another object is to provide new modulation techniques for use withcathode ray tubes.

Another object is to provide a cathode ray tube with special featureswhich increase the maximum modulation rates which may be applied to thetube.

Further advantages and objectives will become clear from thespecification and the drawing wherein:

FIGURE 1 represents a cathode ray tube with a target screen, beamindexing means, and a plurality of radiation detectors. The tube alsocontains special shaping electrodes which are shown schematically.

FIGURE 2 represents a target screen configuration that may be used inthe tube of FIGURE 1.

FIGURE 2a illustrates a cross sectional view of the target screen ofFIGURE 2.

FIGURE 2b illustrates a mesh-like structure that may be used as a targetscreen.

FIGURE 3 represents another target screen configuration that may be usedin the tube of FIGURE 1.

FIGURE 3a illustrates a cross sectional view of the target screen ofFIGURE 3 with three different arrangements for generating index signals.

FIGURE 4 represents one channel of a system embodying a pulse generator,responsive to an indexing radiation from the target screen of a tube,which is used to control the modulation of the electron beam generatedin the tube.

FIGURE 5 represents an idealized excitation of the target screen ofFIGURE 3 when the electron beam is scanned linearly from 0 to 3T andnon-linearly from 3T to 6T.

FIGURE 6 represents another idealized excitation of the target screen ofFIGURE 3 by the electron beam wherein pulses of difierent size orduration are used.

FIGURE 7 represents still another idealized excitation a target screen,with the last strip being of increased dimension and the pulse being ofdifferent size or duration.

FIGURE 8 represents the idealized excitation of one strip of a targetscreen wherein the period of excitation is modulated in time as afunction of amplitude of the signal to be displayed.

FIGURE 9 represents an electrical pulse signal with exponential-likerise and decay. 7

FIGURE 10 illustrates bell-shaped curves representative of the effectsan electron beam have upon an indexing strip.

FIGURE 11 represents an indexing feature of a target screen akin to thatof FIGURE 3.

FIGURE 12 represents a filter-detector combinations suitably responsiveto indexing radiation from the screen of FIGURE 11.

FIGURE 13 illustrates a method of controlling the scanning velocity,shape, and amplitude of an electron beam as a function of videomodulation.

FIGURE 13a illustrates a waveform that may be used in the arrangement ofFIGURE 13 to control the period of excitation of the electron beam as afunction of video modulation.

FIGURE 14 illustrates a minimum time delay system embodying threegridcontrolled photo-multiplier tubes driving a three color single guncathode ray tube.

FIGURE 15 illustrates a special photo-multiplier tube, with threeinputs, three control grids, and a single coaxial line output whichfeeds the gun of a special cathode ray tube.

FIGURE 16 illustrates a plurality of electro-magnetic radiationgatherers and transmitters.

FIGURE 17 illustrates further electro-magnetic radiation gatherers andtransmitters.

FIGURE 18 represents the neck section of a cathode ray tube with aplurality of lenses affixed to the electron .gun structure.

FIGURE 19 represents a cathode ray tube with a target screen forgenerating X-radiation and with detection means for converting theX-radiation into electrical signals.

FIGURE 20 represents a cathode ray tube with two detectors responsive totwo different electro-magnetic radiations.

FIGURE 21 represents a cathode ray tube in which the electron beam isfurnished by the last stage of a secondary emission electron multiplier.

This invention, it will be shown, provides novel cathode ray tubes,target screens, beam indexing means comprised of electromagneticradiation generators and detectors, pulse generators, and videomodulators, interconnected with circuit means in various arrangementsthat provide color television receiver systems. The manner in whichthese systems operate will be understood from the followingspecification taken in conjunction with the drawing.

In FIGURE 1, there is shown a cathode ray tube envelope 10 containing anelectron beam forming member 12. Target screen assembly 14 is scanned bythe electron 'beam furnished by member 12. Coils 16 conventionallyprovide the vertical and horizontal scanning action. Two radiationdetectors 18 are shown located external of the tube. They are X-rayresponsive and are disposed substantially parallel to and near the planeof the target screen assembly 14. Vernier vertical deflection plates 20,and Vernier horizontal deflection plates 22 are disposed to control theelectron beam as hereinafter set forth. Two radiation detectors 24 areshown disposed within the neck portion 26 of the cathode ray tube.Detectors 24 may be used with detectors 18, depending upon the totalnumber of indexing signals being generated as will become clear. Thus,means 18 are shown positioned outside the cathode ray tube and means 24are shown within the tube to detect the electro-magnetic index signals.Means 18 may 'be comprised of suitably responsive photo-multipliers suchas the RCA 931A; means 24 may be comprised of the elements of which the931A consists. Alternatively, the arrangements of FIGURE 19 may be usedwhen one detector is required, and that of FIGURE 20 may be used when aplurality of detectors are required. The target screen assembly 14consists of members 28, and 32. Member 28 in one embodiment, iscomprised of phosphors or other visible radiation emitting materialsarranged in narrow strips which are positioned lengthwise in thevertical direction. The horizontal scanning of these strips takes placesubstantially perpendicular to the thus designated vertical direction.Member 30 is an electron-transparent light-reflecting aluminum layer.Member 32 consists of strips that provide electro-magnetic indexradiation when bombarded by the scanning beam of electrons. Dependingupon the materials that these strips are made of, the electro-magneticindex radiation may extend from waves of infra-red to X-rays. When thisindexing radiation is in the X-r-ay region, members 30 and 32 may beinterchanged, as will be explained infra. In FIGURE 3a a target assemblyis shown Which is capable of generating index signals in the Hertzianrange.

Target screens FIGURE 2 shows, on an enlarged scale of front view of onepossible arrangement of layer 28 of target screen assembly 14. Red,green, and blue color producing phosphors are arranged in the sequencered-green, blue-green and are designated -41, 42-43. The dimensions ofthe phosphor strips that are selected for this purpose are such thatwhen the horizontal scanning beam, which proceeds linearly from left toright across FIGURE 2, is constant in intensity, a substantial whiteimage is presented to the observer. This is achieved by having thewidths of the strips in the path of scan inversely proportional to theluminous efliciencies of the color producing phosphors. Phosphors arepresently available which are more efiicient in the green than in theblue, which is more efficient than the red. Therefore the red strip iswidest, the blue strip is narrower, and the sum of the two green stripsis narrowest. The efiiciencies stated are those which apply when a humanbeing is the observer. The screen strip is divided as shown since thevisual acuity of the eye is greatest in the green region of thespectrum. For detectors other than the eye similar considerationsprevail. Strips 36 and 38 of which layer 32 is comprised, are deposited,or placed on the aluminum layer 30, or on the phosphor layer 28. Thesestrips provide the electro-magnetic index signals. The signal from strip36 is used to excite, via suitable circuitry, the red-green phosphorcombination; the index signal from 38 is used to excite, via suitablecircuitry, the blue-green phosphor combination. The indexing strip is infront of the color producing strips which it is associated so that thescanning time required for the beam to proceed from strip 36 to strip 40is substantially equal to the overall delay that is encountered betweenthe generation of the index signal at 36 and the time that its effect isfelt at strip 40. This time delay is shown in FIGURE 2 as T An equaldelay T is shown to exist between the indexing strip 38 and colorproducing strip 42. For optimum performance the period T should bereduced to a minimum. This may be accomplished by using anelectro-magnetic radiation index signal and by using a minimum number ofwide ban-d circuits.

In FIGURE 2a there is a cross sectional view of one configuration of thescreen of FIGURE 2. The color producing phosphor strips 40, 4 1, 42, 43are illustrated.

The layer 30 of electron-transparent aluminum is also shown. Indexingstrips 36 and 38 are on the side of the screen intended to face the gunof the tube, corresponding to layer 32 of FIGURE 1. Strips 36 mayconsist of suitably prepared Hex ZnO, or Ba SiO activated by lead, or bytriclinic CaMgSiO activated by cerium. When bombarded by the scanningbeam the strip 36 will produce electro-magnetic radiation in theneighborhood of 3700 Angstroms. This radiation has the furthercharacteristic of decaying very rapidly upon cessation of energization.Strip 38 may consist of a tungsten wire, or molybdenum, or othermaterial with high atomic number that generates X-rays upon excitationby the scanning beam. X-ray production is normally encountered when thescanning beam strikes layer 30, and the phosphor strips. It is made toincrease substantially when the beam strikes 38 due to the fact that theefliciency of X-ray production is proportional to the atomic number ofthe metal of which the target is constructed. The governing equationessentially is: Efiiciency=1.4 l0- ZV where Z is the atom number of thetarget, and V is the electron accelerating voltage. For tungsten, Z=74,and at 20 kv. the efficiency is approximately 0.2%. This X-radiationalso decays very rapidly after cessation of energiza'tion; more so thanthe phosphors of which strip 36 may consist. Hence the screen of FIGURE2a may be used to generate two electro-magnetic index signals which aredistinguishable from each other, from the visible display, and fromspurious radiations.

In the event that strip 36 also is preferred to be an X-ray emitter thenit is desirable to make use of the characteristic radiation of the X-rayproducing strips. Molybdenum for example, operated at 20 kilovolts willyield characteristic radiation at 0.71 and 0.63 Angstroms. By suitablefiltering, in the detector or in the screen, it is possible todistinguish the continuous distribution of X-rays produced by thetungsten strip 36, from the characteristic radiation of molybdenum strip38. If it is desired to use a plurality of strips that emitcharacteristic radiation it is necessary to make a selection governed byMoseleys law f /2 :K (2-6) which states that the frequency of thecharacteristics radiation is proportional to the atomic number of theemitter. For example, copper has a K-radiation at 1.53 Angstroms whenexcited by 8 kv. electrons. At 15 kv. this radiation increases much morerapidly than the background, or continuous radiation. The method ofgenerating these characteristic spectra, and of filtering the separateradiations, is well known to those skilled in the use of X-rays. I referto X-rays and Electrons by Arthur H. Compton, 1926, published by D. VanNostrand Company, and to X-rays in Practise by Wayne T. Sproull,published by McGraW Hill, 1946, Tables III, IV and V, for furtherparticulars. Three points will be mentioned here for simplifying theunderstanding of this facet of the invention. First, the characteristicradiation shows up as a sharp peak in the plot of intensity versusWavelength for a particular target. Second, an excitation energy whichexceeds a certain minimum is required to excite these peaks. Third, amaterial that is the same as the target material used in generatingcharacteristic spectra does not have a strong affinity for absorbingsuch characteristic radiation.

In view of the importance of generating these signals alternate meansare illustrated in FIGURE 2b, and in FIGURE 3a. In FIGURE 2b a mesh-likestructure is formed of horizontal members 37, and vertical members 36and 38. The interstices of this structure are filled, strip-wise, withphosphors to provide the color producing strips 40, 41, 42 and 43.Member 36 may consist of a copper wire; member 38 may consist of amolybdenum wire; many other choices exist as was just explained. Themembers 37 may or may not be conductive but should be substantiallydifferent from. 36 and 38 insofar as X-ray producing qualities areconcerned. The conductive assembly is operated at high voltage. It isclear that as the electron beam scans from left to right indexingsignals will be generated. The overall time delay in the circuitry usingthese signals should be adjusted to T and T which represent periods oftime akin to T of FIGURE 2.

In FIGURE 3, a signal indexing strip 44 is shown. The signals derivedfrom 44 will provide gating pulses for energization of the red, blue,and green phosphors. The overall time delay, between generating theindex signal at 44 and energizing the first phosphor strip, is shown tobe T As was stated with respect to FIGURE 2, it is desirable to reducethe overall time delay to a minimum.

In FIGURE 3a a cross section of a target screen configuration is shownwhich will provide three different electro-magnetic index signals.Phosphor layer 28 comprises strips of color emitting phosphors; layer 30is electron-transparent and "light-reflecting; layer 32, also eleca.

tron-transparent, provides continuous X-radiation, and may also providecharacteristic X-radiation. A constant voltage V is maintained at theside of the target screen opposite layer 32. A suitable voltage V ismaintained across layer 32. When the scanning beam of electronstraverses the layer 32, electro-magnetic index signals are generated at44a, 44b, and 44c. The voltage V may be applied by means of atransparent electrical coating. This coating may be applied to member 28or to the faceplate of the tube to which it is to be positioned, oradhered. The voltage V rnray be applied via member 32.

Proceeding to FIGURE 19, the target screen 310 is maintained at thevoltage introduced through lead 308. The inside of the face plate 316 ismaintained at the voltage introduced through 314. Insulators 313separate the target screen from the face plate. When the electrons fromgun 302 pass through screen 310, they will be accelerated ordecelerated, thereby producing electro-magnetic radiation index signals.When these signals are in the X-ray region, the interruption or changein X-radiation may be detected by coating light collecting andtransmitting means 304 with a material such as zinc oxide at 305 whichwill radiate near or in the visible spectrum when excited by X-rays.Means 304 serves as a light pipe to transmit the radiation thusgenerated at 350 to photomultiplier elements 320, 324, 326, whichoperate in a well known manner to yield an electrical signal at 330.Means 304 may have a channel therethrough as at 307 to permit passage ofthe electrons from gun 302 to the target screen. Element 320 convertsthe radiation which is transmitted to it via 304 into electrons forsubsequent multiplication by the secondary emission process.Alternatively, means 304 and the wave-changer 305, may be eliminated byhaving element 320 comprised of a material such as bismuth which willconvert the X- radiation which impinges upon it directly into electrons.

The arrangement in FIGURE 20 provides for two internal detectors ofelectro-magnetic index radiation. Light pipes 350 and 352 are akin to304 of FIGURE 19; detectors 360 and 362 .are akin to 320; dynodes 364,366, 368, are akin to 324, 326, and 328; collector plates 370 and 372are akin to 329. Gun 354 is akin to 302. One electrical index signal isobtained from 370, the other from 372, in order to control the electronbeam furnished by gun 354. This arrangement may be used with the targetscreen of FIGURE 2a. The target screen generates an ultra-violet indexsignal and an X-ray index signal as previously described. Accordingly,element 350 may comprise nickel-oxide glass to transmit the ultravioletsignal and element 352 may comprise fuse silica coated at 351 with zincoxide to convert the X-radiation to a longer wave-length which iscapable of being transmitted through 352. Elements 350 and 352 arepositioned as shown to pick up an amount of radiation from the targetscreen which is substantially independent of the position on the screenof the radiating area.

Returning to FIGURE 3a, the signal at 44a is seen to occur in thefollowing manner. Layer 32. is maintained at 20 kv. and consists of athin layer of copper for example. When layer 32 is scanned by 20 kv.electrons a continuous spectrum, and 1.53 Angstrom characteristicradiation, are emitted. Either, or both, of these signals may bedetected. The region 45 is maintained at V a voltage substantiallydifferent from V This may be accomplished by the transparent coating orby placing a wire grid at 45. The faceplate of tube envelope 10 may alsobe used to provide the grid; or construction as described in my US.Patent 2,885,591 may be used.

The signal at 44b occurs due to the removal of a strip of layer 32. Whenthe electron beam scans this region clearly a change in the X-radiationwill be produced which is detectable.

The signal at 44, as at 440, occurs due to acceleration or decelerationof the electrons. However, the layer 32 is not altered as at 44a, and44b. This may be desirable for production purposes. When X-radiation isaugmented at 47 for indexing purposes in one of the manners previouslyset forth it will be found that the thin, electron transparent layer 32,which is at 44c, will not materially attenuate these X-rays.

Another mode of operation of the target screen at 44c, and at 44a,consists of regulating the velocity change of the electrons, and therate of the velocity change, to produce electromagnetic signals in theHertzian and microwave range. The frequency of these signals iscontrolled by V V and the physical distance between them. FIGURE 17shows an antenna arrangement which may pick up these signals for furtherutilization.

Index signal detector An arrangement is shown in FIGURE 4 which makesuse of the indexing signals generated by the target screen structure ofFIGURE 2. Element 50 is photon-sensitive and emits electrons in responseto bombardment or energization by the electro-magnetic indexing signals.Element 52 is a filter that transmits the radiation from index strip 36,and that attenuates or stops the radiation from index strip 38, and thespurious radiations. By way of example, if strip 36 is Hex Z O radiatingat 3700 Angstroms, and strip 38 is copper radiating 1.53 Angstroms, then52 suitably may consist of a thick layer of nickel oxide glass. Thismaterial will pass the 3700 Angstroms signal, attenuate the 1.53Angstrom signal, and attenuate the spurious X-radiation and the spuriousvisible radiations. Dynodes 54, 56, 58, and operate to increase thesignal represented by the electron flow from element 50 by a process ofsecondary emission amplification. Anode 62 collects the output signalfrom where it is fed to gate 76. After a short time delay, furnished 'byelement 80, the output signal is fed to gate 78. Thus the pulse-likesignal generated by strip 36 will be detected by element 50, amplified,and used to operate gate 76 for the purpose of allowing the red videoinformation to modulate the intensity of the electron beam. Thecumulative time delay in excitation and transmission of theelectro-magnetic index signal; in transmission of the electron signalthrough the dynodes, gate, and to the gun of the cathode ray tube; andin the passage of the intensity modulated electron beam from the gun tothe target screen, is substantially equal to the period T M designatedin FIGURE 2. Element delays the output signal obtained at 62 for a timeequal to that which the scanning beam takes in traversing the red strip40. This delayed signal operates gate 78 for the purpose of allowing thegreen information to modulate the intensity of the electron beam. It isclear that in this manner proper color synchronization is obtained. Asecond photon-sensitive secondary-emission detector-amplifier and gatearrangement are required but not illustrated to operate the blue-greenphosphor combination. Likewise, the method and means for deriving thevideo information are not illustrated as being unnecessary forunderstanding of the present invention. Element 52 in the seconddetector-amplifier combination may suitably consist of a relativelythick layer of copper. This layer 52 clearly will pass the 1.53Angstroms characteristic copper radiation; will attenuate the 3700Angstroms signal emitted by index strip 36; and will attenuate spuriousvisible radiation.

Regenerative Detector It is of interest now to control the delay and theshape of the pulses that operate the gates. This may be achievedconventionally by delay lines, multi-vibrators, blocking oscillators,biased amplifiers, biased gates, etc. The arrangement of FIGURE 4 isnovel for the purposes herein intended. A fast decay phosphor deposit 64is excited by the leading edge of the detected and amplified iexndsignal. Light pipe 66 provides feedback to element 50 to produce apositive feed-back signal. Very rapidly a saturated output signal isobtained at anode 62. A negative going signal is obtained from theoutput of gate 76, or from a delay line akin to 80, which is coupled todynode 58 via capacitor 82. This negative going signal interrupts thepositive feedback path, terminates the output pulse, and thedetector-amplifier is ready to receive a new trigger signal. Element 64may consist of Hex Z O. Element 66 may consist of fused silica. The timeconstants are adjusted in consequence of the pulse width desired. Thefirst dynode 54 may be a grid structure akin to that used in vacuum tubetriodes and by means of voltage source 70 may be adjusted to control thethreshold of operation so that the incident electro-magnetic indexsignal must exceed a minimum value before the triggering signal iseffective. Variable voltage source 72 may be used to control the overalldelay through the dynodes. Variable resistor 74 may be used to controlthe amplitude of the output signal. Since these controls areinter-dependent, they may be ganged together mechanically after initialadjustment to provide for convenient system readjustment by the operatoror technician. Thus, there is provided a fast rise-time pulse generatorwhich responds to the leading edge of the index signal, which respondsto a definite index signal level, and which yields an output pulse offixed width and amplitude. Additionally, if it is desired, the sweep orscanning voltages may be applied to the control elements of this pulsegenerator to compensate for fixed distortions in the electron beamdeflection system.

Modulation of the video signals In FIGURE a base line 84 may beconsidered to represent distance along the target screen of FIGURE 3 inthe direction of the horizontal scan. Pulses 86, 88, and 90 represent inan ideal fashion the excitation of the scanning beam on a target screen.The pulses may be derived from arrangements such as those justdescribed. The intervals from 0 to 6T represent equal time periods. Theintervals also represent the widths of the color phosphor strips asshown. When the scanning beam traverses the screen with constantvelocity from 0 to 3T the pulses 86 are equally spaced and preferablycentered in each interval of space. When the scanning velocity is notconstant, or when the pulse delays introduce error, as shown from 3T to6T, the pulses 86 are advanced to the positions shown by pulse 90, orretarded to the position shown by pulse 88. The pulse width is shownequal to t which in this case is approximately T/ 3. The non-linearityillustrated is t, or T/ 3, for each time period 3T. The errors resultingfrom non-linearity of scan are cumulative for the time betweensuccessive indexing pulses. Therefore, the pulse first derived from theindexing pulse is shown to have a small shift between 3T and 4T, thesecond derived pulse is shown to have a larger shift between 4T and ST,and the last derived pulse is shown with the largest shift between STand 6T.

The illustration in FIGURE 6 teaches how the pulse first derived fromthe indexing pulse may be made of greater duration than the pulse lastderived while still maintaining color purity. This is due to the factthat the accumulated errors of scan position are much less for the firstderived pulse. For the example cited the excitation period may beincreased from t to 2 /3t. Since the red phosphor is least efficient itis clear that doubling the excitation period of this strip is ofconsiderable consequence; and this is achieved without increasing thewidth of the red strip.

The illustration in FIGURE 7 teaches still another method of improvedutilization of variable pulse and phosphor widths and spacings. Here itis clearly shown that by increasing the Width by 33% of the strip whichis excited by the pulse last derived from the index pulse it is possibleto increase the period of excitation of that strip by and still preservecolor purity.

Taking these last two features in combination makes it possible to makeeffective use of 60% of the target screen area even in the presence of a10% non-linear scan. This can be achieved by using pulse widths of 2/31, 1 /st, and 2! (a total of 6t) on the target screen of FIGURE 7where, for example, the red strip may have a width of 3t, the blue strip31, and the green strip a width of 4t (making a total of 10:). As agenerality then, advantage is obtained in broadening the excitationinterval at the start of a pulse train and making the latter derivedexcitation intervals successively more narrow; and in successivelybroadening the width of the individual strips in the direction of scanso that the strip to be excited by the initial pulse in a given train isrelatively narrow in comparison to these which are to be excited bypulses which follow in the train. Clearly these arrangements efficientlyutilize (1) the scanned area of a cathode ray tube and (2) the emissioncurrent of the CRT gun.

The illustration in FIGURE 8 shows that the duration of the targetexcitation pulse may be modulated within the interval 0 to T, making itpossible to use a constant intensity scanning beam. Each color videosignal modulates the duration of the beam within each respective colorstrip so that the duration of excitation is proportional to themagnitude of the information to be presented. The use of a constantintensity scanning beam is of considerable value in maintaining uniformfocus and spot size of the beam. Clearly a combination of intensitymodulation and duration modulation of the beam may also be used toadvantage.

The pulse shapes illustrated in FIGURES 5, 6, 7, and 8 are rectangular.These pulses represent the idealized excitation of the target screen. Inpractice distortion of the idealized excitation is to be expected. Thepassage of a rectangular pulse through delay lines, gates, transmissionlines, etc., can be expected to distort the original pulse. Thisdistort-ion, which is correctable, is a function of the original pulsewidth and shape, and of the bandwidth of the circuits through which thepulse travels. It is also a function of the design of the electron gun.In FIGURE 9 a distorted wave shape is illustrated that might result frompassing a rectangular pulse through circuits with inadequate bandwidth.By use of shaping circuits, Schmitt triggers, blocking oscillators,multivibrators, etc., it is possible to reshape or restore the distortedWaveform so that its effect is lessened. The leading edge of a distortedpulse is shown at 96, the trailing edge at 92. By biasing at 94 it ispossible to re-create a rectangular pulse with a duration 1.

Control of the scanning beam Another source of distortion of theidealized excitation results from the sape of the scanning beam. Anelectron beam that is circular in cross section will have a variation indensity of electrons measured across a diameter that may be representedby curve 96 in FIGURE 10. Were a scanning beam of this shape to scan andenergize a strip that emits indexing radiation it is clear thatsomething less than a rectangular pulse of indexing radiation would beobtained. The extent to which this distortion is detrimental dependsupon many factors and may or may not be serious. I have disclosedpreviously the use of an index radiation generating strip that has anoutput whose magnitude saturates upon excitation; I also disclosed thatthe output of the pulse generator may saturate in amplitude. Both ofthese modes of operation will reduce the distortion caused by thescanning process. Referring back to FIGURE 4, and the explanationthereof, it is seen that the distortion may be still further reduced byusing the leading edge of the index radiation pulse to trigger a pulsegenerator. The stability of this leading edge is of prime importance inthis mode of operation. When the scanning beam is intensity modulatedthe effect of an increase in intensity upon the beam dimensions, or uponits effect, is illustrated at 98 in FIGURE 10. When this situationprev-ails the effect is the same as advancing,-in time, the leading edgeof the index radiation pulse. This will result in jitter of the indexpulses that is a function of the amplitude modulation of the scanningbeam. One method of reducing this jitter is to provide an index stripthat is scanned by a beam whose characteristics are held constant duringscanning of the-index strip. Another method is illustrated in FIGURE 13.

To explain FIGURE 13, reference should first be made to FIGURES 19 and20. Deflection plates 318 and 319 of FIGURE 19 and 356, 358 of FIGURE 20akin to 22 and 20 of FIGURE 1 may be incorporated and utilized when itis desired to vary the shape and position of the electron beam in thecathode ray tube. For example, the horizontal scanning velocity in acolor television system using substantially vertical strips ofphosphorescent materials may be regulated so that the effective timeduring which the electron beam impinges on a particular strip or stripsis considerably longer than would be permissible with a uniform,horizontal scanning velocity. The set of plates orthogonal, or nearlyso, to those imparting the variations in horizontal velocity may beincorporated and utilized when it is desired to elongate the electronbeam in a direction substantially parallel to the aforementioned strips.For equal horizontal and vertical resolution in a color kinescope, ofthe type considered, it is possible to increase the length of theelectron beam transversely of its horizontal travel, or parallel to thevertical phosphor strips, by a factor of the order of 3.1 withoutadversely affecting the ultimate resolution. Furthermore, due to theanticipated correlation in the picture bright areas it is possible toincrease this ratio still further without suffering an undue loss ofresolution. These last set of deflecting plates may be utilized so thatthe spot stretch is controlled by the picture content at the point, orarea, in question.

The arrangement of FIGURE 13 is responsive to an index pulse. The indexpulse may be derived, for example, from the detector-amplifier of FIGURE4 and may be used to control the excitation of the target screen ofFIGURE 2. Pulse 106 is provided by means 110; pulse 108 is provided bymeans 112. Pulse '106 is first derived from the index pulse and is madeto have a greater duration than pulse 108 which is later derived. Pulse106 operates gate 76 which releases the red video signal. This gatedsignal in turn furnishes a positive going pulse of voltage to the grid100 of gun 12. The greater the red video signal the more positivebecomes grid 100 so that the red phosphor strip of FIGURE 2 will beenergized in an amount proportional to the magnitude of the red videosignal. Simultaneously the index pulse is delayed and shaped in means112 to provide a pulse 108 to operate the green gate 78 which in turnreleases the green video signal to intensity modulate the electron beamfurnished by gun 12. The pulses 106 and 108 are fixed in amplitude, andrectangular in shape. The gated video signals will drive the grid morepositive to intensity modulate the beam 114. To reduce the spread of thebeam 114 when its intensity is increased, plates 20 are made positivevia connection 116 by the gated video signals. These plates 20 may be inthe path of the beam as shown or may be part of anode 104. In the latterevent anode 104 would be built in segmented fashion. The positive pulseson plates 20 will stretch beam 114 in the direction perpendicular to thehorizontal scan; this direction is parallel to the phosphor strip longdimension. This stretching will reduce the spread of beam 114 in thehorizontal direction. Should this horizontal spread still be excessive,plates 22 are utilized. These plates are also in the vicinity of gun 12and are connected to retard the velocity of scan in the horizontaldirection when horizontal beam spread occurs. The retardation signal isequal to or proportional to the amplitude of the gated video signals,and thus will cancel the effects of horizontal beam spread insofar asthe timing of the leading edge is concerned. This will reduce leadingedge jitter and provide a more stable electro-magnetic index signal.

For the arrangement of FIGURE 13 to provide a modulation similar to thetype illustrated in FIGURE 8, the means and 112 are selected to providetriangular pulses 118 and 120, or additional pulse shaping elements areadded. The triangular pulses are suitable coupled to the gates. Then,not only will the intensity of beam 114 be increased when the gatedvideo signals increase, but the time duration of the beam will increase.This is illustrated in FIGURE 13a where a video signal level 122 makesthe electron beam effective for a brief interval whereas a strongervideo signal makes the electron beam effective for an interval 124. Theadvantage gained here is that of reducing the intensity variations, andtherefore the focus variations, in the beam 114 from that required withconstant duty-cycle energization of the phospher strips. Other methodsfor converting variable amplitude information into variable pulse-widthinformation are Well known and therefore not described. When using thistype of modulation it may be desirable to provide an index strip whichis energized by a constant intensity scanning beam. This fixed beam maybe obtained by known means.

Reducing the time delay Coming to another aspect of this invention, theoverall time delay, and distortion, in the feedback loop comprising thegun, the target screen, the electro-magnetic radiation, the detector,the amplifier, the gate, and back to the gun, is reduced in thearrangement of FIGURE 14 from that achievable in FIGURE 4 or l3. Alsothe gate is eliminated. The gun 12 provides an electron beam 114.Vernier deflection plates 20 and 22 may be used for the purposes justdescribed. The target screen provides a plurality of indexingradiations; one for each color strip to be excited and controlled. Athree color producing screen is selected for illustrative purposes. Thethree index radiation generators are symbolized in FIGURE 11 at 132, and134. Three index radiation gatherers are shown at 136, 137, and 138.These elements transmit the proper index radiation to means which detectthe radiation to provide an electrical signal, which is amplified, andmodulated to furnish output signals for modulating the beam 114 inaccordance with the video information that is to be viewed on the targetscreen. Three index radiation filters are symbolized in FIGURE 12.Filter 131 attenuates or reflects the radiation from generators b and 0,but passes that from generator a. Filter 133 attenuates the radiationfrom generators a and 0, but passes that from generator b. Filter 135attenuates the radiation from generators a and b, but passes that fromgenerator c. These filters are used in conjunction with the indexradiation gathering, transmitting, or detection means to properlysynchronize the overall operation. For example, element 136 picks up theindex radiation that is to be associated with the energization of thered phosphor strip. This radiation is transmitted through 142 to meansPhoto-sensitive means 144 provides a group of electrons in response toexcitation by the index radiation.

Elements 144, 146, and 148 are arranged to operate as a heaterlessvacuum triode. The emission from 144, the spacing of 146, and 148, andthe voltages impressed thereon are selected to provide a space charge inthe region between 144 and 146. Design details familiar to vacuum tubedesigners can be applied here for construction purposes. The red videosignals are applied to grid 146 to control the passage of electrons from144 to 148. Plate or anode 148 collects the thus controlled electronflow. Plate 148 is unlike an ordinary triode, however, in that it alsobehaves as a dynode and emits secondary electrons. Further stages ofsecondary emission amplification follow such as at 150. The outputsignal is collected at 156 to furnish a negative going pulse signal,158, to the cathode of the gun 12. The time delays are arranged so thispulse signal controls the energization of the red phosphor strip.Voltage 158 may also be fed .to plates 22 to retard the leading edge ofthe index radiation pulse for reasons described previously. To controlincrementally the horizontal scan rate it is desirable to use also thepositive output 160 from element 154 so that the signal on plates 22will be push-pull. The output from -4 may also be used for spot stretchas described previously. Means similar to 140' are symbolized in FIGURE14 for exciting the blue and green color producing phosphor strips.

Instead of introducing the red control voltage as a video signal at 141it is possible to use deflection plates 152 to obtain synchronousdemodulation of the carrier signal and it is otherwise possible to usedirect decoding of carrier type signals but this goes beyond theteachings of the instant invention and will not be discussed further.

In FIGURE 15 means 170 combines the three detectoramplifier-modulatorsof FIGURE 14 into a single device. Elements 174, 176, and 17 8 are akinto elements 143, 145, and 142, respectively. Element 204 is akin to 144.Control grid 190 is akin to control grid 146. Dynodes 200 and 196' areakin to 148 and 150, respectively. Output plate 198 is akin to 156.Elements 206 and 208 furnish electron groups in response to theexcitation by radiation of the green and blue index strips respectively.Member 202 provides optical and electrical shielding. Member 192 is acontrol grid that is connected to the green video signals. This gri-d192 regulates the passage of electrons from 206 to plate 200. Likewise194 is a control grid that is connected to the blue video signals. Thisgrid 194 regulates the passage of electrons from 208 to plate 200.

The operation of means 170 follows from the description of operation ofFIGURE 14. Three electro-magnetic index signals are generated,collected, filtered, and brought to impinge upon three differentphoton-sensitive electronemitting surfaces. Each index signal andelectron-emitting surface is associated With a different color producingphosphor. Each electron-emitting surface furnishes a copious supply ofelectrons which are space charge limited. A control grid is provided foreach supply of electrons. Each grid is connected to its associated colorvideo signal to control the passage of these electrons. The electronsare passed in individual groups, sequentially, and are amplified by aseries of dynodes. The amplified and controlled electron group arecombined in the dynode stage to provide a series of signals as theoutput.

It is 'to be noticed that the successive dynodes may be reduced inphysical size, as depicted, to reduce associated capacitances, toincrease the potential frequency response of the output signals, and tohelp match element 198 to its transmission line. Thus, the output plate198 of means 170 conveniently feeds into a coaxial cable 172. Thecoaxial transmission line carries the series of signals to the cathoderay tube for modulation of the scanning beam contained therein. Thescanning beam excites the target screen. Electro-rnagnetic index signalsare generated, and the process continues.

The advantages gained in simplicity of construction and in performanceare numerous. For example, the time delays and distortions may bereduced from the arrangement of FIGURE 14. Still additional significantadvantages occur by constructing the gun 12, in FIGURE 15, of thecathode ray tube in planar \fashion, with coaxial input connections at210, and with a resistor at 212 which efiectively matches the impedanceof coaxial transmission line 172. Thereby a reflection-less terminationfor the output of means may be provided. This arrangement clearlyprovides for improved transmission and utilization of very short pulses.Resistor 212 may be cylindrical or annular. Alternatively, the internalimpedance between the grid cathode may terminate the transmission line.Elements 214 are illustrated to indicate that means similar to plates 20and 22 may also be used.

Wide-band cathode ray tube The construction of FIGURE 15 also drawsattention to the fact that the conventionally heated cathode of gun 12of the cathode ray tube may be eliminated. Plate 198 may be fabricatedto be secondary emissive. With this arrangement the plate 198 may yieldthe electrons normally furnished by cathode 218. Grid 220 of gun 12 mayalso be dispensed with, since the output at 198 is properly modulated;i.e., its amplitude is proportional to the intensity of the image pointto be displayed. The dotted outline of a tube envelope 230, anddeflection coils 216, are shown to symbolize this mode of operation.Although not shown, it is clear that the pulse generator of FIGURE 4 maybe incorporated into the embodiment of FIGURE 15 to provide pulses ofsaturated space charged clouds of electrons which are then gridcontrolled by the video signals.

The arrangement of FIGURE 15 that yields the heaterless cathode isillustrated more clearly in FIGURE 21. Two of the index signal paths areshown. The numeration of elements in FIGURE 21 akin to those in FIG- URE15 remain the same.

Radiation collectors In FIGURE 16 a lens 250, a cone-shaped member 252,and a hollow cone 254 are illustrated. These devices may be used to pickup and transmit electro-magnetic index radiation in the range frominfra-red to ultra-violet. Flat fresnel type lenses may also be used. InFIGURE 17 a lens 256 with a hole therethrough, and a rod 258, aredevices that may be used for the same purpose. Rod 258 may be solid; ifhollow it may be made of metal. Antenna 260 is connected to a coaxialtransmission line 262 and may be used to extend the range of indexradiations, that are picked up and transmitted to microwave and toHertzian waves. To extend the range of signals that may be picked upinto the X-ray region members 250, 252, 254, 256, or 258 may be coatedwith a material, such as Hex Z O, as described heretofore.

In FIGURE 18 electro-magnetic radiation gatherers 250 are shown affixedto the electron source 12 of the cathode ray tube. Any of the pick-upelements may be so affixed.

Summary Thus, it has been shown and described how a plurality ofelectro-magnetic index signals may be generated that indicate theposition of a scanning beam on a directed ray tube. A plurality of meansare disclosed for synchronizing the energization of the scanning beam wth the target screen upon which it impinges. A plurality of means aredisclosed for modulating the scann ng beam; this modulation beingdirected towards presenting information on the tar-get screen, and beingdirectedtowards insuring proper synchronization. In combmation withthese features are additional means that reduce the time delay in systemsynchronization and means that increase the band width handlingcapabilities of cathode ray tubes.

It is to be Stated that although this invention is described in a colortelevision display system it is not limited thereto. The use of the Wordcolor encompasses other than visible radiations in a properinterpretation of this invention. Many electro-magnetic radiations maybe used, it being clear that each radiation may serve as a separatecommunication or control channel. In the case of radiation in thevisible range optical techniques for filtering the radiations are wellknown; in the microwave, or Hertzian, range electrical filteringtechniques are also well known; in the X-ray region techniques forproducing and filtering monochromatic radiation are likewise well known.In addition to the Compton and Sproull references already cited, I alsorefer to Applied XRays, by Clark, McGraw Hill, 1955. The wide range ofsignals, that may be utilized constitutes one advantage of thisinvention. It isalso to be noted that these teachings can be applied tostorage-type devices, to projection tubes, to digital signal generators,to quantizers, etc. In applications utilizing the scanning of a beamrelative to a target where high speeds, high definition, wide bandwidths, and minimum distortions are required, this invention providesits greatest advantages.

Having thus described my invention, I claim:

1. A beam-index multi-color display system comprising:

(1) a target screen having a plurality of different color-emittingregions disposed for scanning in sequence by a scanning beam;

(2) index-signal source means responsive to the scanning of the targetscreen for providing an indication of the position of the beam on saidscreen;

(3) color signal source means;

(4) signal processing means, responsive to (a) the color signals and (b)to the index signals, for controlling the scanning beam so as toproperly excite the color-emitting regions;

said scanning beam, target screen, index-signal source means, and signalprocessing means having an inherent overall time delay;

(5) means for precisely controlling the time delay to effectuateregistry of the scanning beam on selected color-emitting regions, and

(6) scanning beam modulating means in the signal processing means,responsive to the magnitude of the different color signals, forelongating said beam in proportion to the intensity of the particularcolor signal to be displayed.

2. The system of claim 1 including a cathode ray tube which provides thetarget screen and an electron gun for furnishing the scanning beam.

3. The system of claim 1 wherein said target screen comprises means forgenerating electromagnetic radiation index signals.

4. The system of claim 1 wherein said index-signal source meanscomprises means for detecting electromagnetic radiation index signals.

5. The system of claim 3 wherein said index signals are in the X-rayregion of the spectrum.

6. The system of claim 1 wherein the time delay is equal to the timerequired for the scanning beam to traverse two adjacent color-emittingregions.

7. The system of claim 1 wherein the time delay is less than the timerequired for the scanning beam to traverse two adjacent color-emittingregions.

'8. The system of claim 2 wherein said target screen comprises coloremitting strips disposed vertically with respect to the horizontalscanning action of the electron beam; including means for scanning theelectron beam across the target screen; and wherein the scanning beammodulating means comprises a pair of electrodes for stretching theelectron beam in a vertical direction.

9. The system of claim 8 including means for coupling the color signals,applied to the control grid electrode of the electron gun, to the pairof electrodes for stretching the electron beam.

10. A high-speed beam-index multi-color display system comprising:

(1) a target screen having a plurality of different color-emittingregions disposed for scanning in sequence by a scanning beam;

(2) index-signal source means responsive to the scanning of the targetscreen for providing non-sinusoidal pulse-like index signals indicativeof the position of the beam on said screen;

(3) color signal source means;

(4) signal processing means, responsive to (a) the color signals and (b)to the index signals, for modulating the scanning beam into a sequentialtrain of pulses, each pulse thereof generally having a duration which isless than the time required for the beam totra'verse the strip withwhich the pulse is associated;

said scanning beam, target screen, index-signal source means, and signalprocessing means having an inherent overall time delay which is a smallpart of a line scansion;

(5) means for precisely controlling the time delay to effectuate properregistry of the pulses of the scanning beans on the color-emittingregions, and

(6) scanning beam modulating means in the signal processing means,responsive to the magnitude of the different color signals, forincreasing the duration of pulses in said train of pulses in proportionto the intensity of the particular color signal to be displayed.

11. The system of claim 10 including a cathode ray tube which providesthe target screen and an electron for furnishing the scanning beam.

12. The system of claim 10 wherein said target screen comprises meansfor generating electromagnetic radiation index signals.

13. The system of claim 10 wherein said index-signal source meanscomprises means for detecting electromagnetic radiation index signals.

14. The system of claim 12 wherein said index signals are in the X-rayregion of the spectrum.

15. The system of claim 10 wherein the time delay is equal to the timerequired for the scanning beam to traverse two adjacent color-emittingregions.

16. The system of claim 10 wherein the time delay is less than the timerequired for the scanning beam to traverse two adjacent color-emittingregions.

17. The system of claim 10 wherein the color-emitting regions are narrowstrip-like elements disposed so as to be scanned substantially at rightangles to the long dimension.

18. The system of claim 10 wherein the signal processing means modulatesthe pulses of the scanning beam into a series of non-sinusoidalrectangular-like time varying pulses.

19. The system of claim 10 wherein the signal processing means formodulating the scanning beam into a sequential train of pulses comprisesmeans, responsive to the different color signals, for elongating thescanning beam in proportion to the intensity of the particular colorsignal to be displayed.

20. The system of claim 1 including means in the signal processing meansfor modulating the scanning beam into a sequential train of pulses sothat pulses thereof have a duration in time proportional to theintensity of the particular color signal to be displayed.

References Cited by the Examiner UNITED STATES PATENTS 2,434,196 1/1948Cawein 31514 2,458,891 1/1949 Boyle 3 l531 2,784,342 3/1957 Van Overbeek1785.4 2,930,931 3/1960 Aiken 3l5--31 DAVID G. REDINBAUGH, PrimaryExaminer. I. A. OBRIEN, Assistant Examiner.

1. A BEAM-INDEX MULTI-COLOR DISPLAY SYSTEM COMPRISING: (1) A TARGETSCREEN HAVING A PLURALITY OF DIFFERENT COLOR-EMITTING REGIONS DISPOSEDFOR SCANNING IN SEQUENCE BY A SCANNING BEAM; (2) INDEX-SIGNAL SOURCEMEANS RESPONSIVE TO THE SCANNING OF THE TARGET SCREEN FOR PROVIDING ANINDICATION OF THE POSITION OF THE BEAM ON SAID SCREEN; (3) COLOR SIGNALSOURCE MEANS; (4) SIGNAL PROCESSING MEANS, RESPONSIVE TO (A) THE COLORSIGNALS AND (B) TO THE INDEX SIGNALS, FOR CONTROLLING THE SCANNING BEAMSO AS TO PROPERLY EXCITE THE COLOR-EMITTING REGIONS; SAID SCANNING BEAMTARGET SCREEN, INDEX-SIGNAL SOURCE MEANS, AND SIGNAL PROCESSING MEANSHAVING AN INHERENT OVERALL TIME DELAY; (5) MEANS FOR PRECISELYCONTROLLING THE TIME DELAY TO EFFECTUATE REGISTRY OF THE SCANNING BEAMON SELECTED COLOR-EMITTING REGIONS, AND (6) SCANNING BEAM MODULATINGMEANS IN THE SIGNAL PROCESSING MEANS, RESPONSIVE TO THE MAGNITUDE OF THEDIFFERENT COLOR SIGNALS, FOR ELONGATING SAID BEAM IN PROPORTION TO THEINTENSITY OF THE PARTICULAR COLOR SIGNAL TO BE DISPLAYED.